Closed loop control system with automatic variation of its regulating feedback amplification

ABSTRACT

In a closed-loop control system the regulated system portion has a number (n) of integration members. The regulator feedback which is connected between output and input of the regulated system portion comprises regulator control means for automatically adapting the amplification of the regulator to variations in amplification occurring in the regulated system portion during operation of the latter. The regulator control means comprise a first differentiating stage of the (n+1)-th order, an at least partial analog of said regulated system portion, a quotientforming divider having two inputs of which one is connected through the first differentiating stage to the output of the regulated system portion and the other is connected through the analog to the input of the regulated system portion. A second differentiating stage is connected with the analog and adapted for phase coincidence of the two signals at the respective two inputs of the quotient-forming divider.

United States Patent Speth [54] CLOSED LOOP CONTROL SYSTEM WITHAUTOMATIC VARIATION OF ITS REGULATING FEEDBACK AMPLIFICATION [72]Inventor: Winirietl Speth, Erlangen, Germany [73] Assignee: SiemensAktlengesellsehatt, Berlin, Germany [22] Filed: Dec. 17,1969 [21]Appl.No.: 885,691

[15] 3,655,954 [4s] Apr. 11,1972

Primary Examiner-Eugene G. Botz [57] ABSTRACT In a closed-loop controlsystem the regulated system portion has a number (n) of integrationmembers. The regulator feedback which is connected between output andinput of the regulated system portion comprises regulator control meansfor automatically adapting the amplification of the regulator tovariations in amplification occurring in the regulated system portionduring operation of the latter. The regulator control means comprise afirst differentiating stage of the (n+l)-th order, an at least partialanalog of said regulated system portion, a quotient-forming dividerhaving two inputs of which one is connected through the firstdifferentiating stage to the output of the regulated system portion andthe other is connected through the analog to the input of the regulatedsystem portion. A second differentiating stage is connected with theanalog and adapted for phase coincidence of the two signals at therespective two inputs of the quotientforming divider.

16 Claims, 9 Drawing Figures [30] Foreign Application Priority Data Dec.20, 1968 Germany ..P l8 15 964.3

[52] U.S.Cl. ..235/150.l,3l8/6l5,318/561 [51] Int. Cl. ..G05b 17/02,0063 7/ l 8, G069 7/48 [58] FieldoiSearch .;235/l50.l,150.2;3l8/56l,3l8/6l5 [56] Relerences Cited UNITED STATES PATENTS 3,241,027 3/1966Albright ..3l8/56l REBULAYUR u n I l I I I y :1 DAIUM VALUE 1 1 ll 1IW-Xl-AMPLIFIER llllilllEll RElllILATEll SYSTEM H 7 lllFFERElllIAlillBnausea #muum CLOSED LOOP CONTROL SYSTEM WITH AUTOMATIC VARIATION OF ITSREGULATING FEEDBACK AMPLIFICATION My invention relates to closed-loopcontrol systems whose forward path, constituting the main system portionto be regulated, has its output feedback-connected with its input forcontrolling or regulating the input quantity in dependence upon thedelivered output quantity.

More specifically, the invention concerns closed-loop systems whoseregulated main or forward portion comprises between input and output anumber (n) of integration members, and has for its object to provide,during operation of this regulated system portion, an automaticadaptation of the regulating feedback amplification to changes inamplifying gain occurring in the regulated system portion.

Before further dealing with the invention proper, the following isoffered as background information and for the purpose of definition.

A closed-loop control system, also called feedback control system, iscomposed of two component portions, namely a controlling or regulatingportion and a controlled or regulated system portion, the latterconstituting the forward path of the quantity being regulated. Forexample, if the regulated quantity is steam pressure, the regulatedsystem (main portion of the entire organization) includes the pressuresupply and the pressure control valve from which this component systemextends to the pressure output point at which the regulated steampressure is to appear. The valve or other control member constitutes abranch point and responds to a command signal from the controlling orregulating system which includes a feedback from the output side of theregulated system to the branch point. The command signal varies thesetting of the control member and thereby changes the quantity passingthrough the regulated system (forward path). At some point of the loopor at several points, or along a stretch of the loop, there may beintroduced one or more disturbances, and these have a falsifying effectupon the control of the regulated system in which they become in effectamplified in the sense of a multiplication. That is, the controlmagnitude as well as any disturbance affecting the flow of thecontrolled quantity in the regulated system are much smaller inintensity than the changes in the quantity thus subjected to control,this resulting in the justmentioned amplifying effect occurring in theregulated system.

Relative to the terminology used in this specification and to theservo-type of block diagrams shown in several illustrations of theaccompanying drawings, reference may be had to Feedback Control Systemsby Gille, Pelegrin and Decaulne, McGraw-l-lill Book Co., New York, 1959,pages 7 to 22 and 77 1; also to Analysis of Feedback Control Systems" byBruns and Saunders, McGraw-Hill Book Co., New York, 1955, pages 1 to 6,208 and 226; and to "Elektronische Analogiegeraete by Dietrich Ernst,published in the German periodical Regelungstechnik", Vol. 6, 1958, Nos.3 to 6.

The regulated quantity is either the ultimate quantity itself (alsocalled actual or real quantity), such as the pressure of the steam to becontrolled or regulated in the example selected for illustration above,or the voltage of a regulated electrical system. However, the regulatedquantity may also be constituted by some other physical quantity,usually an electrical voltage, that varies in proportion to, or in someother definite dependence upon, the ultimate quantity to be regulated.For example, if the steam pressure in the abovementioned example ismeasured electrically, a voltage varying in proportion to the actualsteam pressure may constitute the "regulated quantity in the meaning ofthe present disclosure; or if the speed of a vehicle is the actualquantity to be controlled or regulated, the speed-proportional voltagefurnished from a tachometer generator may serve as the regulatedquantity". Because of the applicability of such secondarily variablequantities, the regulated quantity is often called pilot quantity ormagnitude, regardless of whether or not it is the actual" or real"quantity. The datum or reference quantity is indicative of the value atwhich the regulated (pilot,

real, or actual) quantity is to be maintained and is sometimes called"pattem quantity, especially if it can be set to any chosen value, forexample by adjusting a potentiometer or if it is varied in accordancewith a given time program or with a change in temperature or otherparameter.

It is necessary, as a rule, to adjust'the regulating system (feedback)to the parameters of the regulated system (controlled forward path) forattaining the best feasible dynamic transfer function of the looporganization. If the loop amplification varies during operation, aregulating system initially optimalized may no longer provide optimalregulating performance but may become maladjusted to changed parametersof the regulated system.

it is known that optimal regulation requires that the amplification inthe regulating system (regulator) of the closedloop organizationmaintain a definite ratio to the amplification occurring in theregulated (forward path) system of the organization. If the regulatedsystem is subjected to operationally occurring disturbance effects, forexample variations in temperature, the amplification of the regulatedsystem portion may change so that the desired ratio is no longermaintained. It has been found that of the various disturbing influences,only those will change the regulated-system amplification that operatein a multiplicative sense, whereas disturbing influences acting only inan additive sense, such as most load disturbance magnitudes, do not havesuch an effect.

It is therefore a more specific object of my invention to provideclosed-loop regulating system organizations with automatically operatingmeans which identify the change in forward-path amplification stemmingfrom multiplicatively acting disturbance influences, and which thenimpose upon the amplification of the regulator (i.e. the feedback orregulatingsystem portion) of the organization an effect that compensatessuch change in regulated-system amplification.

lt is known for similar purposes to continually subject the regulatedsystem to given test signals in order to achieve an identification ofits path parameters. When this method is applied to a regulated systemwhile this system is in operation, the regulated quantity is alwaysmodified by an effect stemming from the superimposed test signal.Although this effect can be kept slight, it may nevertheless causeundesired disturbances. Furthermore, this method must carefully providefor always uniform test signals, and this, as a rule, involves aconsiderable amount of additional equipment and expense.

It is, therefore, a further object of my invention to perform theabove-mentioned identification, without the use of test signals, byutilizing the regulated-quantity signal appearing at the end of theregulated (forward-path) system.

A more specific object of the invention is to filter out of theregulated-quantity signal any disturbances that act additively upon theregulated-system path, even if the regulated system contains one or moreintegration members.

To achieve these objects, and in accordance with my invention, relatingto a closed-loop control organization in which the regulated system(forward path) has a number (n) of integration members and which has aregulator system feedback-connected between output and input of theregulated system, comprises regulator control means for automaticallyadapting the amplification of the regulator to the variations inamplification occurring in the regulated system during operation of thelatter. The regulator control means comprise a first differentiatingstage of the (n+1 )-th order, and an at least partial analog, such as asubstitute circuit network, of the regulated system, further aquotient-forming divider stage which has one of its two inputs connectedthrough the first differentiating stage to the output of the regulatedsystem, the other input being connected through the analog to the inputof the regulated system. A second differentiating stage is connectedwith the analog to provide for phase coincidence of the two signals atthe respective two inputs of the quotient-forming divider stage.

It is the fundamental concept of this invention to have thedifferentiating stages operate to eliminate from the regulated quantitysignal those disturbing effects that act additively upon the regulatedsystem; and to place the thus filtered signal into relation with anin-phase signal occurring at the end of a signal path which is impressedby the control quantity (output signal of the regulating feedbacksystem) and which is a disturbance-free model (analog) of the regulatedsystem.

The second differentiating member is of the first order when theregulated system does not contain an integrating member (n=); generally,the order of the first differentiating member, depending upon the typeof regulated-system analog being used, is determined by the requirementthat on the analog signal path up to the quotient-forming stage thecontrol signal must be subjected to the same frequency characteristic asalong its path through the regulated system and the integrating memberfollowing the regulated system. It is essential that with thisidentification of the regulatedsystem amplification, the result isobtained independently of the magnitude of the operationally occurringcontrol-signal magnitude, and that'it is not necessary to know thefrequency of occurrence, type and point of attack of the individualdisturbance magnitudes themselves.

According to a further feature of the invention, it is preferable toarrange the second differentiating member ahead of the regulated-systemanalog, seen in the signal propagation direction. This is ofsignificance if the regulated-system analog contains at least oneintegrating member. In this case, the regulated system itself wouldpossess at least one integrating member (n 9* 0), and hence thecontrol-signal quantity in the stationary state (fully regulatedcondition without error signal) would not be zero but would have tocompensate the load. Consequently, if the control-quantity signal weredirectly impressed upon the input of the regulated-system analog, avirtually infinitely large control range would have to be provided forthe integrators of the regulated-system analog. However, if thedifferentiating member is disposed ahead of the regulated-system analog,the integrators of the analog are affected only by changes of thecontrol-quantity signal so that a finite control range for theintegrators is sufficient.

Further objects, advantages and features of my invention will bedescribed in, and will be apparent from, the following description ofembodiments of closed-loop regulating systems according to the inventionillustrated. schematically and by way of example on the accompanyingdrawings in which:

FIG. 1 shows the diagram of a complete feedback control system in arelatively simple over-all configuration.

FIG. 2 is the diagram of a similar system equipped with a more elaborateregulator (feedback portion) than the system of FIG. 1.

FIG. 3 shows diagrammatically a third embodiment of a completeclosed-loop regulating system.

FIG. 4 exemplifies the circuit diagram of a differentiating memberapplicable in any of the systems shown in FIGS. 1 to FIG. 5 is a circuitdiagram of a differentiating member applicable in a system as shown inFIG. 3.

FIG. 6 is a diagram of a memorizing quotient-forming stage applicable inany of the systems shown in FIGS. 1 to 3.

FIG. 7 is a diagram of another modification of a memorizingquotient-forming stage, also suitable for systems according to FIGS. 1to 3.

FIG. 8 is a logic circuit diagram of an integrating device composed ofdigital component suitable as an integrator in devices according toFIGS. 6 and 7.

In FIG. 1, a regulator R furnishes an output signal y which constitutesthe control magnitude for varying the quantity passing through theregulated system (forward path) S of the illustrated closed-looporganization. The regulated quantity 1 appearing at the output of theregulated system portion S (hereinafter simply called regulated system)is compared at the input of the regulator R with a datum magnitude w.The result, constituting the error signal or deviation, is supplied tothe regulating amplifier 10 of the regulator R. In the examplerepresented in FIG. 1, the regulated system S comprises twotime-constant members 2 and 3 and a dead-time member 1; that is, theregulated system S in this example does not contain an integratingmember (n=0). It is assumed that before and behind the individualregulating-system members 1, 2 and 3, multiplicatively actingdisturbances K1, K2, K3 are effective, as well as additively actingdisturbances L1, L2 and L3, the rate of change of all of thesedisturbances being small in comparison with those of the other variablequantities of the closed-loop organization. Among the multiplicativelyacting disturbance influences there may be operational changes inamplification in the regulated-system members 1, 2 and 3.

' Onlythe multiplicatively acting disturbance effects falsify the FIG. 9exemplifies by a schematic diagram a function generator suitable for usein a quotient-forming stage according to FIG. 7.

The same reference characters are applied in the various illustrationsfor corresponding items respectively. The system components shown onlyby block symbols are known as such, for example from the literaturementioned above.

amplification of the regulated system S, and the product of theseeffects is to be identified with the aim of eliminating the influence ofdisturbance magnitudes K1 to K3 by an opposing variation in amplifyinggain of the regulator R.

For this purpose, the regulated quantity x is passed through adifferentiating member 4 to the input terminal 5 of a divider, i.e; aquotient-forming stage 6, the terminal 5 beingcoordinated to thedividend input as contrasted to the divisor input terminal 8. A secondsignal path is provided for the control quantity y and extends through afurther differentiating member 7 and an analog or substitute circuit(image) M of the regulated system S to the divisor input 8 of thequotient former 6.

The regulated-system analog M is a complete model of the regulatingsystem S differing therefrom only by the fact that no'operationaldisturbance effects L1 to L3 and K1 to K3 act upon the model. Thedifferentiating members 4 and 7 have the same rating and are both of thefirst order. They serve to keep the signals x,, and x, at the quotientformer 6 free from the influence of the additively acting disturbancesL1 to L3.

The signals at, and x,, are in phase with each other. As can beconfirmed by an analysis of the frequency characteristic of the twosignal paths for the control quantity y up to the respective inputs 5and 8 of the quotient former 6, the quotient x /x at any momentprecisely corresponds to the product K=K1- K2-K3 of all disturbancequantities acting multiplicatively upon the regulated system S. If theamplification of the regulator R is influenced in inversely proportionalrelation to the magnitude K, for example as illustrated in FIG. 1 by adivider device denoted by 11, then any operational variation of K or theactually effective regulating-system amplification is exactlycompensated by a counteracting change in regulator amplification. Theregulating loop organization as a whole thus remains continuouslyoptimized.

In the embodiment shown in FIG. 2, the regulated system S contains anintegrating member 12 with the frequency characteristic l/pT (n=l Such aregulating system would cor-, respond, for example, to that of adirect-current drive energized through current rectifiers, in which casethe dead-time member represents the statistical running time of therectifier, the time-constant member represents the armature circuit, andthe integrating member represents the mechanical fiywheelmass of themotor. As in the embodiment of FIG. 1, it

7 in FIG. 1. Another differentiating member of the second order isprovided in the parallel signal path for the control quantity signal y,and consists of the series connection of two differentiating members 14and 15. The output signal of the differentiating member 15 is applied toa complete but disturbance-free analog M of the regulating system S. Thesignal x appearing at the output of the differentiating member 13 andthe signal x,, appearing at the output of the analog M are in phase witheach other and, due to the filtering action of the differentiatingmembers employed, do not contain any components stemming from theadditively acting disturbance magnitudes L. In distinction from theembodiment of FIG. 1, the signal x is supplied to the dividend input 5of the quotient-forming stage 6, whereas the signal x,, is supplied fromthe output of the differentiating member '13 to the divisor input 8.Consequently, at the output terminal 9 of the quotient fonner 6 therewill appear a magnitude l /K which is inversely proportional to theproduct K of the multiplicative disturbance effects and which actsthrough a multiplier 16 to vary the amplifying gain of the regulator Rin analogy to the variation effected in the embodiment of FIG. 1. Asaresult, any variations in regulated-system amplification arecompensated.

The parallel signal path of the control quantity y can be simplified bytaking advantage of the fact that the series connection of adifferentiating member and an integrating member is equivalent to amechanically simpler proportionality member. Such a simplification isalso embodied in the system according to FIG. 2. As shown, there are twoswitches 17. When these are shifted from the illustrated horizontalpositions to the vertical positions, the analog M is inactive and issubstituted by an analog M, and the differentiating member 15 having anidealized frequency characteristic pB is substituted by a proportionalcharacteristic member 18 having the amplifying factor V=B/ T. Thesubstituted analog M does not contain the analog of the integratingmember 12, in this respect being also simpler than the completeregulated-system analog M. A corresponding simplification is obtainedgenerally for n integrating members in the regulating system S asfollows. The regulated system signal x is filtered by means of adifferentiating member of the (n+1 )-th order and thus converted to asignal x,, in which the components stemming from additive disturbancesignals are eliminated. The signal x,,, to be compared with the filteredsignal x must have the same phase as the latter. This is the case if thefrequency characteristics of the two signal paths available to thecontrol-quantity signal y up to the respective inputs 5 and 8 of thequotient former 6 differ only from each other by a constant factor. Forthat reason, a differentiating member of the (n+1 )-th order is alsoincluded in the parallel signal path of the control magnitude y thatcontains the complete regulating-system analog M, and a differentiatingmember up to the n-th order is branched-off therefrom and is connectedtogether with a corresponding number of integrating members of theregulating-system analog so as to obtain a member of purely proportionalcharacteristics. Actually, therefore, the parallel signal path to beprovided for the control-quantity y need, in the extreme, contain onlyone differentiating member of the first order and an analog M of theregulated system no longer containing any integrating member. Inpractice, it will depend upon individual requirements whether it ispreferable to entirely eliminate the integrating members in this manneror whether they are to be only partly omitted from the regulating-systemanalog.

As far asdescribed, it has been ignored that ideally differentiatingfilters having the transfer functions shown on the drawing for themembers 4, 7, 13, 14, 15 and 18 are not in practice obtainable andconsequently do not have the ideal frequency characteristic pB. Inreality, the frequency characteristic of the differentiating filter isalways of the form pB/( 1+ pA) in which A and B are constantcoefficients and p jw denotes the frequency. The term l+pA is called theparasitic denominator of the differentiating member.

FIG. 3 shows a practically applicable form of the differentiatingmembers in a modification which results when the two switches 17 in FIG.2 are placed from the illustrated horizontal to the vertical positions,except that the quotientforming stage 6 in FIG. 3 does not provide thequantity UK but the quantity k, and that the latter quantity is to actin inverse proportion upon the amplification of the regulator R. Thedifferentiating member 13 of the second order, connected between theterminals 20 and 21 in FIG. 3, is shown to consist, for example, of theseries connection of two differentiating members of the first order andof the above-mentioned kind, thus exhibiting the frequencycharacteristic p -B /(l+pA). The series connection in the parallelsignal path of the differentiating member 14 as well as of theproportional member 18, according to FIG. 2, is obtained by providing adifferentiating member of the first order having the frequencycharacteristic pB/( l+pA) and a time delay member having the frequencycharacteristic pB/( l+pA), so that the differentiating member 19 betweenterminals 22 and 23 has the resultant frequency characteristic p'B/T(l+pA) Consequently, the

parasitic denominators of the two differentiating members 13 and 19 areequal. The regulated-system analog M does not contain the analogon 12'corresponding to the integrating member 12 of the regulated system S;the two signals x,, and x are in phase with each other and can be placedinto quotient relation to each other for automatic adjustment of theregulator amplification.

It should be noted that for the purposes of the invention thetime-constant coefficients A and B can be chosen entirely at will, itbeing only essential that in the example illustrated in FIG. 3 theregulated quantity x be subjected twice and the control quantity y onlyonce to differentiation. In the division, the parasitic denominators aswell as the coefficients B cancel each other so that, independently ofthe course of the controlquantity signal y as well as of the specificdesign of the differentiating members, as long as they meet theabove-mentioned requirements, the magnitude available at the outputterminal 9 of the quotient-forming stage 6 will always correspond to theactually occurring amplification of the regulated system S.

FIG. 4 illustrates an example of electrical circuitry for thedifferentiating member 13 (FIGS. 2, 3) which is composed of passiveelectrical components only. This member consists of an RCdifferentiating network formed of two capacitors C1 and two ohmicresistors RI.

FIG. 5 illustrates an electrical circuit design of the differentiatingmember denoted by 19 in FIG. 3 and comprises an input network C2, R2which is a differentiating network corresponding to that of FIG. 4,whereas the component network composed of the resistor R3 and thecapacitor C3 constitutes a time delay network. The resistors R2, R3 andcapacitors C2 and C3 can be dimensioned in accordance with conventionalrules so that, in consideration of the integrating time T of theintegrating member 12 (FIG. 2) contained in the regulated system S, thefrequency characteristics of the differentiating members 13 and 19 meetthe above-mentioned requirements. Of course, the necessary frequencycharacteristics of the two differentiating members 13 and 19 may also besecured with the aid of active electrical components, that is, by meansof operation amplifiers known from analog computer techniques andemploying the methods usual with analog computers.

In each of the system embodiments so far described with reference toFIGS. 1 to 3, the two input signals at the quotientforming stage 6, uponchanges of the control magnitude y, differ from zero and in most caseswill decay while oscillating about the zero value. Since these twosignals are in phase with each other, both will several times vanishsimultaneously during identification, and at these moments the signalissuing (at terminal 9) from the quotient-forming stage will beindefinite or indeterminable, or in any event would not reliablycorrespond to the instantaneous regulated-system amplification. It istherefore also a more specific object of my invention to avoid suchuncertainties.

For this purpose, and in accordance with another feature of myinvention, the closed-loop organization is provided with aquotient-forming stage which, upon vanishing of its input signals storesthe output signal. This can be done in a particu larly simple manner byproviding the quotient-forming stage of the system organization with anintegrator in negative feedback connection with a multiplier. Althoughother signal-storing means are applicable for the same purpose, the onejust described results in particularly simple equipment.

If the regulated system may operate under stationary conditionsthroughout long periods of time, this being expectable especially with aso-called fixed-magnitude (on-off) regulation, the regulated quantity(x) may not change for long periods of time and consequently the inputsignals of the quotient-forming stage will exhibit the zero value forcorrespondingly prolonged periods. To make certain that thequotient-forming stage will provide a correspondingly extended storingof the previously processed output signal, and according to a furtherfeature of my invention, the integrator contained in thequotient-forming stage may be designed as a digital digital counterwhich is preceded by a voltage-frequency converter and followed by adigital-analog converter.

FIG. 6 shows an embodiment of such a memorizing quotient-forming stage,in which in the event of simultaneous disappearance of its inputquantities x and x at the respective terminals 5 and 8, the previouslydetermined quotient x /x is stored and thus remains frozen. This isessentially achieved by the storing ability of an integrator 24, which,upon disappearance of its input signal, retains its output signal. Theinput signal of integrator 24 consists of the output signal of anamount-forming stage 25 which receives the magnitude x, as the dividendand whose block symbol in FIG. 6 represents the relation a lel betweenits output magnitude a and its input magnitude e. A negative feedbacksignal is subtracted at a mixing point 26 from the output signal of theamount-forming stage 25. The subtracted signal is constituted by theoutput signal of a multiplier 27 which has one input impressed by theoutput magnitude of the integrator 24 and whose other input receives theoutput signal of anotheramount-forming stage 28, the input of stage 28receiving the quantity x,,,. The output signal of the integrator 24 doesnot change its value when its input quantity is equal to zero, that is,when there obtains the relation x K-x,,,, wherein K is the outputquantity of the integrator 24. When the values of .r and x,,, differfrom zero, the output signal of the integrator will automatically adjustitself upon the value K x /x when the quantities x,, and x,,,simultaneously vanish, the above-mentioned relation is likewisesatisfied, and the previously determined value of K is retained as theintegrator output signal. Preferably, the integrating time T of theintegrator 24 is chosen sufficiently short so that the quotient K Je /xis always rapidly available.

Since a reliable identification may be doubtful at very minute inputsignals of the quotient-forming stage 6 (FIGS. 1 to 6), my inventionpursues the further object of suppressing such minute input signals.

According to another feature of the invention, therefore, the output ofthe voltage-frequency converter is preferably connected with the inputof an AND-gate whose other input is connected to the output of athreshold-quantity sensor impressed by the input magnitude of thevoltage-frequency converter.

The input quantities of the quotient-forming stage 6 which are to beplaced in ratio relation to each other, oscillate at the same phase andhence have alternating polarities. The identification of theregulated-system amplification, however, depends only upon the scalaramount of these magnitudes. Consequently, and as described withreference to FIG. 6, the input quantities for the quotient-forming stagecan be passed through amount-forming members onto the input of theintegrator and of the multiplier. However, if the input magnitude thatarrives at the quotient forming stage from the regulated system,contains a noise signal or another periodic highfrequency spurioussignal, such undesired signal content would be rectified by anamount-forming member and thus could falsify the result of theidentification.

further multiplier arranged in the input circuit of the integrator formodulating the integrator input voltage in dependence upon theinstantaneous polarity or in dependence upon polarity as well asamplitude of this input quantity. As a result, spurious signals of theabove-mentioned kind no longer reach the input of the integrator inrectified condition and are suppressed by the storing efiect of theintegrator. In this arrangement, the correct regulating sense in theregulating circuit, composed of the integrator and the multipliernegatively feedback-connected with that integrator, is obtained in asimple manner, and there is the possibility of increasing the operatingspeed of the quotient-forming stage at low input signals.

In cases where the integrator is realized by means of analogtypecomponents and an indefinitely long storability is not required, it isadvantageous according to another feature of my invention, to apply tothe integrator a slight and constant additional feed voltage leading toa definite limit, so that in stationary operation at vanishing inputsignals of the quotientforrning stage the integrator will remain at adefinite limit stop so chosen that the output signal of thequotient-forming stage then is set to the maximally possible regulatoramplification. In this waiting setting, i.e. up to the occurrence of thenext change in control-quantity signal, the regulator remains adjustedto highest sensitivity. Consequently, when the next regulating departureoccurs, the regulator exhibits a particularly rapid starting phase ofoperation up to attaining the fully regulated state (disappearance ofthe deviation or error).

The features and improved results just mentioned apply to the embodimentshown in FIG. 7 illustrating a memorizing quotient-forming stage which,in systems generally corresponding to FIGS. 1, 2 or 3, is applicableinstead of the embodiment according to FIG. 6. The integrator 24 and itsnegative feedback by means of a multiplier 27 are retained so that astoring of the result is secured in the manner described with referenceto FIG. 6. In distinction to the embodiment of FIG. 6, however, themagnitudes x,,, and x themselves rather than their scalar amounts actupon the input and negative feedback of the integrator 24. Contrary toFIG. 6, any superimposed high-frequency noise contained in the inputsignal x,, is not rectified by the action of the amount-forming stage 25but reaches as a superimposed alternating quantity the input of theintegrator 24 and is smoothed or suppressed by the storing effect ofthis inegrator as long as the inverse value of the integrating time T ofthe integrator 24 is sufficiently short relative to the noisefrequencies present, which as a rule is the case. Since the quantitiesx,, and x may exhibit alternating polarities, the change in polaritysign of the two quantities occurring simultaneously on account of theirphase concidence, a change in sign of the quantity x causes inversepoling of the integrator input signal so that the regulating sense ofthe regulating circuit, composed of the integrator 24 and the twomultipliers 27 and 29, does not change. The above-mentioned reversal inpolarity of the integrator input signal is produced with the aid of afunction generator 30 whose input terminal 43 receives the quantity x,,,and whose output, appearing at terminal 44, is applied to one of the twoinputs of the multiplier 29. The other input of this multiplier receivesthe difference between the input signal x,, and the output signal of themultiplier 27.

For securing the correct regulating sense, the function generator 30would have to perform no more than the function of reversing thepolarity. Hence its characteristic could have the course indicated by adot-and-dash line on block symbol 30 in FIG. 7, in which case thefunction generator would act as a flip-flop amplifier. For adaptation tothe input signal amplitudes, however, it is preferable if the functiongenerator 30 has the hyperbolic characteristic shown by full lines onthe block symbol. For an input signal 2 below the small threshold values, this characteristic is described by the relation a c-sign(e), whereinc is a constant and which characteristic for input signals exceeding thethreshold value, is represented by the hyperbolic relation a=l/e,wherein represents the output quantity of the function generator 30. Theintegrator 24 thus receives an input quantity which becomes independentof the amplitudes of the signals x,, and x and depends only upon theratio of these signals. The working speed of the integrator, i.e. thetime elapsing until its output signal corresponds to the desired ratio,is always the same, assuming that during the period of time underconsideration, the effect of disturbing quantities is constant at largeand small amplitudes of the input quantities x,, and x,,,. The mentionedhyperbolic characteristic of the function generator 30 thus secures aconstant identification time.

When in the stationary state of the regulated system S, the controlquantity y has remained constant for a prolonged period of time, bothinput quantities x and .x,,, become equal to zero. If the integrator 24is constituted by analog means, for example with the aid of anelectronic amplifier having a capacitive negative feedback, it mayhappen that the output voltage of the integrator will drift atuncontrollable slow rate to one or the other stable state. To preventthis, a slight constant additional feed-in quantity 2. at the mixinglocality 31 is provided and leads the output of the integrator 24 to adefined limiting stop denoted by 32, at which stop the output signal ofthe integrator 24 exhibits a small value only slightly differing fromzero. This limit stop can be provided in known manner with the aid oflimiting diodes at the output of the integrator 24.

When the output quantity of the integrator is located at this limit, thequantity K is adjusted to its lowest possible value and consequently theamplification gain of the regulator to its largest possible value. Inthis condition, the regulator amplification would be adjusted to a muchhigher gain than required by the optimizing criterion and higher thanwould be permitted by the stability conditions. This, however, has nodisad vantageous consequences as long as the control quantity y does notchange. With each change of the control magnitude, that is, with theoccurrence of a new regulating departure between the datum value W andthe regulated quantity x, a very small additional signal z isoverpowered by the now appearing input signals x or x,,,; the quotientformer again comes under the influence of these quantities and thensufficiently rapidly identifies the actual value of the regulated-systemamplification with the corresponding reduction with the regulatoramplification down to the value provided for the optimal regulatingperformance, thus avoiding sufficiently early the danger of theregulating circuit becoming instable. It has been found that by virtueof this amplification of the regulator, intentionally set excessivelylarge in the stationary state, as well as by the subsequent setting downto the correct value as soon as the stationary state vanishes, a muchfaster full regulation in the event of regulating departures or errorsis obtained than with a regulator which, relative to its amplifyinggain, has permanently the optimal adaptation to the regulated system.This will also be understood from the fact that the speed at which anyoccurring regulating departure will be eliminated, will in principle, behigher, the higher the regulator amplification is chosen. Hence, if atthe beginning of a regulating operation the maximally attainableregulator amplification is applied, such amplification if permanentlyeffective being most likely the cause of oscillations with increasingamplitudes, and when such maximal regulator amplification is reducedsufficiently early to the value needed for stable optimal operation,then the regulating performance in totality is apt to take less timethan when this reduced value of regulating amplification had been ineffect from the very start.

If it is considered disadvantageous that the integrator 24 requires acertain amount of time for performing the identification, that is if itis desirable at any moment to have the quotient X /X available as ameasure of the regulated-system amplification, then a modification canbe used which results from the one shown in FIG. 7 by closing anadditional connection between the terminals 33 and 34, and by openingthe switch 35. The performance of this variant will be understood if oneconsiders that a quantity containing at any moment a magnitudeproportional to the ratio x /x is already present at the end of thesignal path leading through the function generator 30 and the multiplier29, i.e. at the output of the multiplier 29. That is, the signalappearing at the terminal 33, in view of the hyperbolic conversion bythe function generator 30, is represented by x /x K, wherein Kdesignates the instantaneous output signal of the integrator 24. If,therefore, at a mixing locality 36 the output signal of the integrator24 is added, then the voltage at the terminal 9 corresponds at anymoment to the ratio x /x The variant just described, therefore, affordsimmediate identification as well as storing of the integrator outputsignal in the event the input signals at terminals 5 and 8 vanishsimultaneously.

FIG. 8 shows an integrating device composed of digital components whichis applicable as integrator 24 in systems corresponding to FIGS. 6 and 7and which is completely free of drift. The device of FIG. 8 comprises avoltage-frequency converter 37 which converts an analog input voltageapplied to the terminal 33 into a sequence of pulses whose sequencefrequency is proportional to the input voltage. The pulses act upon oneinput of each of two AND-gates 38 and 41, whose second inputs areconnected to the output signals of a threshold-value member 39. It isthe purpose of the threshold member 39 to block the AND-gates 38 and 41when the input voltage at terminal 33 has amplitudes below a thresholds, but to open the gates for the pulses of the voltage-frequencyconverter 39 whenever the input-signal amplitudes are above thethreshold value. Such a blocking of very small input amplitudes may bepreferable in view of the fact that at too small input signals areliable operation of the quotient-forming stage would be doubtful. Theoutput of the AND-gate 38 is connected to the forward counting input ofa bi-directional counter 40. The output of the AND-gate 41 is connectedto the reverse counting input of the same counter 40 and is effective atnegative amplitudes of the input voltage applied to the terminal 33. Thecounter 40 thus operates as a digital storer. Its output magnitude isconverted in a digital analog converter 42 due to an analog voltagesignal which appears at the output terminal 9.

According to a further feature of the invention, the abovementionedfunction generator for modulating the integrator input voltage maysimply consist of an amount-forming stage followed by an invertingamplifier circuit, a switching amplifier being provided for reversingthe poling of the output signal of the inverting amplifier in dependenceupon the polarity of the input signal at the amount-forming circuit. Theinverting amplifier itself can be realized by means of an amplifier of ahigh amplifying gain impressed by a constant voltage and having itsoutput signals limited to maximal positive and negative values, amultiplier being arranged in the negative feedback branch of thehigh-gain amplifier and impressed by the output signal of theamount-forming member. The amount-fonning member may simply be composedof the series connection of an inverting amplifier with a diode, asecond diode of the same forward direction being connected in parallelto the series arrangement of amplifier and first diode.

With the above-described amplitude modulation of the integrator inputvoltage, the integrator input voltage increased by the magnitude of theintegrator output signal can be employed as the output signal of thequotient-forming stage which acts upon the regulating-systemamplification. In this manner, a particularly rapid identification andconsequently an especially rapid adaptation of the regulating-systemamplification can be secured.

FIG. 9 illustrates an example embodying the last-mentioned combinationof features of the invention in a function generator applicable in lieuof the one denoted by 30 in FIG. 7. In accordance with the symbolism ofanalog-computing techniques, electronic amplifiers in FIG. 9 arerepresented by a triangular symbol in which the appertaining amplifyingfactors are indicated. The input magnitude x applied to the inputterminal 43 is first supplied to an amount-forming stage composed of twodiodes 45, 46 and a reversing amplifier 47. The output signal Ix l' ofthe amount-forming stage acts upon one of the two inputs of a multiplier51 which forms part of a negative feedback coupling for anotheramplifier 48. The input quantity of the amplifier 48 is a constantdirect voltage U. Consequently, the output of the amplifier 48 furnishesa quantity proportional to the inverse value of the scalar amount ofx,,,. The quantity I, further acts upon the flip-flop amplifier 49 whichin turn actuates a switching member constituted in the illustratedexample by a polarized electromagnetic relay 50. In accordance with thepolarity of the input magnitude x the output signal of the amplifier 48,representing an inverse value amplifier, is supplied to the terminal 44either directly or with reversed poling, so that the function shown inthe block symbol 30 of FIG. 7 will occur at the output terminal 44 independence upon the input signal. The indicated output limitation at theamplifier 48 secures defined maximal output voltages for small values ofx below a given threshold value which in FIG. 7 is denoted by s, whereasat larger values of x the output voltage of the amplifier 48 willdecrease hyperbolically.

As will be seen from the embodiments described in the foregoing, systemorganizations according to the invention operate by automaticallycounteracting any departure of the regulated-system amplification fromthe predetermined value defined by the constant amplification of theregulated-system analog. As a consequence, there is also achieved aremarkable improvement in facility with respect to the dimensioning ofthe regulator and the avoidance of the often rather time-consumingadjusting expedients for the initial starting-up of the regulating loopsystem. This is because amplification of the regulated-system analog canbe fixed to a presumed value without knowing the amplification of theregulated system itself. It is advisable to select for this purpose anyamplifying value located in the range of changes in regulated-systemamplification. In other words, it is possible to adjust the regulatorfrom the outset in accordance with the estimated value of any selectiveoptimizing criterion under consideration. When thereafter the regulatingloop system is put into operation, the departure of the actualregulated-system amplification from the originally assumed value isidentified by the equipment according to the invention in the samemanner as if a disturbing quantity were active; and the action thenresulting upon the regulator amplification then takes care ofcompensating for the departure. Empirical adjustments at theinstallation site thus are minimized or virtually eliminated.

It has further been found that the analog of the regulated system neednot be highly accurate, especially any regulatedcircuit members ofhigher order can be approximated by analog members of lower orderwithout appreciable detriment to the intended functioning of the systemaccording to the invention.

To those skilled in the art, ti will be obvious upon a study of thisdisclosure, that my invention permits of various modifications and usesother than those particularly illustrated and described herein, withoutdeparting from the essential features of my invention and within thescope of the claims annexed hereto.

I claim:

1. In a closed-loop control system comprising a regulated system portionhaving a number (n) of integration members, a regulator, and a regulatorfeedback-connected between the output of said regulated system portionand the input of said regulator, the combination of regulator controlmeans for automatically adapting the amplification of the system to thevariations in amplification occurring in the regulated system portionduring operation of the latter, said regulator control means comprisingsaid regulator, a first differentiating stage of the (n+l)-th order, andat least two partial analogs of said regulated portion, aquotient-forming divider stage having an output and two inputs of whichone is connected through said first difierentiating stage to the outputof said regulated system portion to receive therefrom a regulated signalthrough said first difi'erentiating stage, a second differentiatingstage, said other input of said divider stage being connected to theinput of said regulated system portion through said analogs and saidsecond differentiating stage for supplying said other input with amodified regulated-system input signal phase coincident with said outputsignal at said respective divider inputs, said output of said dividerstage being connected to said regulator.

2. In a system according to claim 1, said regulator comprising means forreceiving an error signal and having an amplification control stageconnected to said regulated system portion to furnish said input signalthereto, said control stage having an amplification controlling inputconnected to said output of said divider stage to receive a controlsignal therefrom.

3. In a system according to claim 1, said regulator comprising aquotient forming stage having an output connected to said regulatedsystem portion to furnish said input signal thereto, said stage of saidregulator having two inputs and means for applying an error signal toone of them, said other input of said regulator stage being connected tothe output of said divider stage to receive a control signal therefrom.

4. In a system according to claim 1, said second differentiating stagebeing series-connected with said analog and arranged ahead of saidanalog in the propagating direction of said input signal 5. In a systemaccording to claim 1, said quotient-forming divider stage having meansfor storing the stage output signal upon vanishing of its input signals.

6. In a system according to claim 5, said signal storing dividercomprising a multiplier and an integrator forming a negative feedback ofsaid multiplier.

7. In a system according to claim 6, said integrator comprising adigital counter, a voltage-frequency converter preceding said counter inthe signal flow direction, and a digital-analog converter following saidcounter.

8. In a system according to claim 7, said integrator comprising twoAND-gates having respective inputs connected to the output of saidvoltage-frequency converter, and a threshold sensor controlled by theinput of said voltage-frequency converter and having an output connectedto respective other inputs of said AND-gates, and means connecting therespective outputs of said AND-gates to said digital-analog converter.

9. A system according to claim 6, comprising two amountforming membersconnected ahead of, and passing respective input signals to, saidintegrator and said multiplier respective ly.

10. A system according to claim 6, comprising constantvoltage meansconnected to said integrator for supplying thereto an additionalconstant feed voltage to thereby set a given limit for said integrator.

11. A system according to claim 6, comprising a second multiplier havingtwo inputs and an output of which one input and the output are connectedin the input circuit of said divider stage, a function generatorconnected to said feedbackconnected multiplier of said integrator andcontrolled by said modified regulated-system input signal for modulatingthe integrator input voltage in dependence upon the polarity of saidvoltage.

12. In a system according to claim 11, said function generatorcomprising an amount-forming stage, an inverse-valueamplifier infollower connection with said amount-forming stage, a switchingamplifier connected to said inverse-value amplifier for reversing thepolarity of the output signal in dependence upon the input signal ofsaid amount-forming stage.

13. In a system according to claim 12, said inverse-value amplifiercomprising a high-gain amplifier with constant voltage supply means andhaving output signals limited to positive and negative maxirna, saidhigh-gain amplifier having a negative feedback circuit, and a multiplierconnected in said feedback circuit and having a control input connectedto the output of said amount-forming stage of said function generator.

14. in a system according to claim 13, said amount-forming saidintegrator.

Stage of Said f i generator f P f inverting 16. In a system according toclaim 9, said amount-fonning plifier and a diode in series connectionwith each other.

15. In a system according to claim 13, said quotient-forming 22 3::figgmi s fi 23:? amplifier and a dlode m series divider stage having aquotient output signal constituted by 5 the integrator input signalincreased by the output signal of

1. In a closed-loop control system comprising a regulated system portionhaving a number (n) of integration members, a regulator, and a regulatorfeedback-connected between the output of said regulated system portionand the input of said regulator, the combination of regulator controlmeans for automatically adapting the amplification of the system to thevariations in amplification occurring in the regulated system portionduring operation of the latter, said regulator control means comprisingsaid regulator, a first differentiating stage of the (n+1)-th order, andat least two partial analogs of said regulated portion, aquotient-forming divider stage having an output and two inputs of whichone is connected through said first differentiating stage to the outputof said regulated system portion to receive therefrom a regulated signalthrough said first differentiating stage, a second differentiatingstage, said other input of said divider stage being connected to theinput of said regulated system portion through said analogs and saidsecond differentiating stage for supplying said other input with amodified regulated-system input signal phase coincident with said outputsignal at said respective divider inputs, said output of said dividerstage being connected to said regulator.
 2. In a system according toclaim 1, said regulator comprising means for receiving an error signaland having an amplification control stage connected to said regulatedsystem portion to furnish said input signal thereto, said control stagehaving an amplification controlling input connected to said output ofsaid divider stage to receive a control signal therefrom.
 3. In a systemaccording to claim 1, said regulator comprising a quotient forming stagehaving an output connected to said regulated system portion to furnishsaid input signal thereto, said stage of said regulator having twoinputs and means for applying an error signal to one of them, said otherinput of said regulator stage being connected to the output of saiddivider stage to receive a control signal therefrom.
 4. In a systemaccording to claim 1, said second differentiating stage beingseries-connected with said aNalog and arranged ahead of said analog inthe propagating direction of said input signal
 5. In a system accordingto claim 1, said quotient-forming divider stage having means for storingthe stage output signal upon vanishing of its input signals.
 6. In asystem according to claim 5, said signal storing divider comprising amultiplier and an integrator forming a negative feedback of saidmultiplier.
 7. In a system according to claim 6, said integratorcomprising a digital counter, a voltage-frequency converter precedingsaid counter in the signal flow direction, and a digital-analogconverter following said counter.
 8. In a system according to claim 7,said integrator comprising two AND-gates having respective inputsconnected to the output of said voltage-frequency converter, and athreshold sensor controlled by the input of said voltage-frequencyconverter and having an output connected to respective other inputs ofsaid AND-gates, and means connecting the respective outputs of saidAND-gates to said digital-analog converter.
 9. A system according toclaim 6, comprising two amount-forming members connected ahead of, andpassing respective input signals to, said integrator and said multiplierrespectively.
 10. A system according to claim 6, comprisingconstant-voltage means connected to said integrator for supplyingthereto an additional constant feed voltage to thereby set a given limitfor said integrator.
 11. A system according to claim 6, comprising asecond multiplier having two inputs and an output of which one input andthe output are connected in the input circuit of said divider stage, afunction generator connected to said feedback-connected multiplier ofsaid integrator and controlled by said modified regulated-system inputsignal for modulating the integrator input voltage in dependence uponthe polarity of said voltage.
 12. In a system according to claim 11,said function generator comprising an amount-forming stage, aninverse-value amplifier in follower connection with said amount-formingstage, a switching amplifier connected to said inverse-value amplifierfor reversing the polarity of the output signal in dependence upon theinput signal of said amount-forming stage.
 13. In a system according toclaim 12, said inverse-value amplifier comprising a high-gain amplifierwith constant voltage supply means and having output signals limited topositive and negative maxima, said high-gain amplifier having a negativefeedback circuit, and a multiplier connected in said feedback circuitand having a control input connected to the output of saidamount-forming stage of said function generator.
 14. In a systemaccording to claim 13, said amount-forming stage of said functiongenerator comprising an inverting amplifier and a diode in seriesconnection with each other.
 15. In a system according to claim 13, saidquotient-forming divider stage having a quotient output signalconstituted by the integrator input signal increased by the outputsignal of said integrator.
 16. In a system according to claim 9, saidamount-forming stages comprising an inverting amplifier and a diode inseries connection with each other.